JP2022003798A - Antenna having frequency selective element - Google Patents

Abstract

To provide a wide range antenna system that can recognize a large number of frequencies.SOLUTION: An antenna 200 includes: a substrate; and a plurality of leg elements 210, 220, and 230 formed on the substrate. The leg elements 210, 220, and 230 are made of conductive ink, and the leg elements 210, 220, and 230 form a continuing route. At least one of the leg elements 210, 220, and 230 is separately selectable or removable to change the resonance frequency of the antenna. The at least selected one of leg elements 210, 220, or 230 form an antenna route length for the resonance frequency. The antenna may be an energy harvester.SELECTED DRAWING: Figure 2

Description

Cross-reference to related applications This application claims priority to US Non-Provisional Patent Application No. 15 / 944,482, entitled "Antenna with Frequency-Selective Elements," filed April 3, 2018. This document is 1) filed on April 5, 2017, entitled "Power Management in Energy Harvesting," US Provisional Patent Application No. 62 / 481,821, 2) filed on April 7, 2017. Also, US Provisional Patent Application No. 62 / 482,806 entitled "Dynamic Energy Harvesting Power Archive" and 3) US Provisional Patent Application No. 62 / 482,806, filed May 18, 2017, entitled "Carbon-Based Enterna". Claim the priority of patent application No. 62 / 508,295. All of these documents are incorporated herein by reference for all purposes.

As data tracking and mobile communication are incorporated into a wide variety of products and activities, wireless devices have become an important part of society. For example, is the radio frequency identification (RFID) system embedded in objects such as products being transported, vehicles passing through transit points, inventories in warehouses or on assembly lines, and even animals and humans? It is commonly used for tracking and identification via an RFID tracking device that is worn. The Internet of Things (IoT) is another area where wireless devices are used. In this area, networked devices are connected together to communicate information with each other. Examples of IoT applications include smart devices, smart homes, voice-controlled assistants, wearable technologies, and monitoring systems such as those for security, energy, and the environment.

Many applications require these wireless electronic devices to be very small and portable, which limits the ways in which they can be powered, and energy harvesting (EH) is often due to the device. It is used as an additional energy source for. Energy harvesting is, in general, the process of obtaining energy from a variety of energy sources that radiate or emit energy intentionally, naturally, or as a by-product or side effect, by means of energy harvesting components or devices. Is. Types of energy that can be harvested include electromagnetic (EM) energy, solar energy, thermal energy, wind energy, salt gradient, and kinetic energy, among other energies. For example, a temperature gradient occurs in the area around the operating combustion engine. In urban areas, large amounts of EM energy are present in the environment for radio and television broadcasts. Energy harvesting circuits or devices are therefore in these regions or environments, even if the energy levels from these types of energy sources may be highly variable or unreliable. It can be placed above or proximally to take advantage of the presence of these energy sources. Antennas can be used to obtain radio frequency (RF) energy from EM sources such as mobile phones, WiFi networks, and televisions. Energy harvesting is generally distinguished from the direct supply of energy provided by a utility company through a dedicated, wire-connected power transmission line, such as that provided to a particular customer through the grid. To. Each of these is a power load added to the energy source.

In some situations, the energy available for harvesting is also known as background, ambient, or supplemental energy. These energies are not specifically intended to be transmitted to any particular customer or receiver for the purpose of feeding the receiving device. An example of background or ambient energy is natural EM radiation, which is emitted as an unavoidable side effect or by-product of many types of electrical devices or transmission lines. Radio frequencies emitted from ground, air, or satellite radio transmitters, in contrast, may be intended to be used by receivers for long-distance communication purposes, but that radio frequency. Energy, which is EM radiation, can also be used for unintended energy harvesting purposes. In these "unintentional" situations, the energy harvesting circuit simply obtains ambient energy whenever or wherever available, without additional power added to the energy source. In other situations, a dedicated wireless EM energy transmitter can be provided for EM radiation that is widely broadcast or emitted in a particular direction. Here, an energy harvesting circuit or device is known to exist for intentional harvesting or acquisition by the energy harvesting circuit or device, thereby for a particular electrical device. Provide an "intentional" wireless power transfer system. However, in terms of energy harvesting circuits or devices, intentional EM radiation from EM energy transmitters is surrounding (intentional), except that the intentional situation can lead to a more reliable source of energy. Is not) equal to or similar to energy. Both intentionally transmitted energy and unintentionally transmitted energy can be used for energy harvesting.

The energy collected is generally small, usually wireless, usually autonomous, electronic circuits, components, or those used in wearable electronic devices and some types of wireless sensor devices or networks. Obtained for use by the device or stored for future use. For this reason, energy harvesting circuits or devices are typically low energy electronic circuits or devices that are electrically connected, incorporated, or otherwise associated with energy harvesting circuits or devices. Provides a very small amount of power for electronic devices. These energy harvesting circuits are usually auxiliary power sources for the battery on the device, as the EH source does not provide sufficient power or stable power for the entire device.

Antennas play an important role in the ability to harvest energy efficiently. The development of antennas for energy harvesting, as well as antennas for communication in wireless and IoT devices, minimizes size, improves efficiency, achieves multiband frequencies, and offers a variety of antenna materials. In order to study, it is related to research. Antennas are embedded in housings for mobile devices, in embedded devices, and on smart cards and packaging. RFID antennas are often attached on the surface of labels for packaging or labeling, such as small peel-off labels. Some antennas are manufactured by printing such as silk screen printing, flexographic printing, or inkjet printing. Silver inks are the most commonly used inks for conductive components, but carbon inks and polymer-based inks are also used. As wireless devices become more widespread, there is a constant need for more efficient and cost-effective antennas.

In some embodiments, the antenna system has a substrate and an antenna on the substrate, the antenna having a plurality of leg elements. The plurality of leg elements include conductive ink and form a continuous path. At least one of the plurality of leg elements can be individually selected or excluded to change the resonant frequency of the antenna, and the selected leg elements form the antenna path length corresponding to the resonant frequency. do.

In some embodiments, the energy harvesting system includes an antenna system and an electronic circuit. The antenna system includes a substrate and an antenna on the substrate. The antenna has a plurality of leg elements, the plurality of leg elements including carbon-based conductive ink and forming a continuous path. Each of the multiple leg elements can be individually selected or excluded to change the resonant frequency of the antenna. The selected leg elements form the antenna path length corresponding to the resonant frequency. The electronic circuit has a connection to each of the plurality of leg elements, wherein the electronic circuit short-circuits the first leg element of the plurality of leg elements with respect to the second leg element. Is configured to dynamically exclude the first leg element from the plurality of leg elements.

In some embodiments, the antenna system comprises a substrate and an antenna on the substrate. The antenna has a plurality of leg elements, which are provided with conductive ink and form a continuous path. The first leg element of the plurality of leg elements has a first resonance frequency threshold that depends on the received frequency and the first electrical impedance of the first leg element. The first electrical impedance is based on material properties selected from the group consisting of magnetic permeability, dielectric constant, and conductivity. The first leg element can be individually excluded so as to change the resonant frequency of the antenna by changing the antenna path length, and the first leg element has a received frequency of the first frequency. If it is greater than the threshold, it is passively excluded from the antenna path length by making it inactive.

1A and 1B are diagrams showing antenna polarization known in the art. 2A and 2B are side sectional views of an antenna having a frequency selectivity element according to some embodiments. 3A and 3B are side sectional views illustrating the use of material tuning for selecting or excluding leg elements of an antenna, according to some embodiments. FIG. 4 is a perspective view of a flat inverted-F antenna with material tuned leg elements, according to some embodiments. FIG. 5 is a perspective view of a flat inverted-F antenna with leg elements with digital tuning, according to some embodiments. 6A-6C are graphs of antennas and S-parameters for leg elements with digital tuning, according to some embodiments. FIG. 7 is a graph of S-parameters showing customization of resonance frequency according to some embodiments. 8A and 8B are a plan view and a side sectional view of a microstrip antenna capable of printing a dielectric material according to some embodiments. FIG. 9 is a diagram showing a flat inverted-F antenna and the gain response of the antenna according to some embodiments. FIG. 10 is a diagram showing a wavy antenna and a gain response of the antenna according to some embodiments. 11A-C. 11C are diagrams showing a flat antenna printed on a box, according to some embodiments. 12A and 12B are a perspective view and a side sectional view of a bent inverted-F antenna incorporated in a three-dimensional substrate according to some embodiments. FIG. 13 is a perspective view of an L-slot dual-band flat inverted-F antenna according to some embodiments. FIG. 14 is a perspective view of a printed, bent inverted-F antenna according to some embodiments. FIG. 15 is a perspective view of another flat inverted-F antenna according to some embodiments. FIG. 16 is a perspective view of a rectangular, electromagnetically coupled patch antenna according to some embodiments. FIG. 17 is a schematic diagram of a process for manufacturing a printed, selective antenna according to some embodiments. FIG. 18 is a flow chart of a method for manufacturing a printed, selective antenna system according to some embodiments. FIG. 19 is a graph of electrical resistance for conductive materials printed on various paper substrates known in the art. FIG. 20 is a block diagram of an electronic circuit for selecting and excluding frequency-selective antenna leg elements according to some embodiments. FIG. 21 is a graph of frequency response for various antenna configurations according to some embodiments.

The present disclosure describes a printed antenna with multiple leg elements. In this antenna, leg elements can be individually selected or excluded so that they are active for the desired frequency. By utilizing different parts of the antenna, the path length of the antenna, i.e., the part of a given antenna pattern that is active, can be adjusted to capture energy for a particular frequency. That is, the antenna has a dynamically changeable resonant frequency, in which the antenna element is switched in and out to change the path length. This antenna system operates as a wideband antenna capable of recognizing many frequencies. In this antenna, the system finds out which frequency is the predominant source of power and modifies the components and elements of the antenna system to maximize the power received.

In some embodiments, the selection of leg elements occurs passively by tuning each leg element to have a particular electrical impedance. This particular electrical impedance leads to a resonant frequency threshold above which the leg element no longer responds. Tuning of electrical impedance can be achieved by adjusting the materials used to print the leg elements, such as using inks with different electromagnetic permeability, dielectric constant, and / or conductivity. .. The type of material used to make the leg element can also be varied to affect the frequency response characteristics of the antenna. When the antenna receives a certain frequency, the leg element becomes active if the received frequency is below the threshold of the resonance frequency of that particular leg element and becomes inactive if the received frequency is above the threshold. .. Thus, the total path length of the active leg element at a given time point changes the overall resonant frequency of the antenna.

In another embodiment, the selection of leg elements occurs dynamically by electronically switching the leg elements of the short circuit together, thereby excluding the leg elements and reducing the antenna path length. Electronic switching is achieved by electronic circuits such as microprocessors coupled to the leg elements of the antenna.

In some embodiments, the tunable resonant frequency of the leg element can be achieved by the learning shape of the antenna element, such as by using tapered segments. In some embodiments, the dielectric material can also be printed between the leg elements of the antenna to adjust the capacitance of the entire antenna.

In some embodiments, the antenna of the present invention can be configured as a two-dimensional flat design. The flat antenna can extend on one or more surfaces of the object formed of the substrate, such as a transport box.

In a further embodiment, the antenna itself has a three-dimensional (3D) learning shape built into the substrate. The 3D antenna has a plurality of conductors printed on the components of the substrate. Here, each component is coupled and laminated together to form a substrate. This 3D antenna specifically utilizes the 3D characteristics of the substrate material, such as the multi-layered structure of the wavy cardboard and the 3D characteristics of the wavy layer itself. Embodiments of 3D antennas can increase the surface area of a two-dimensional (flat) design antenna. Larger surface areas increase the amount of energy that can be harvested and / or improve reception and transmission for communication. The 3D antenna can also be tuned to operate at different frequencies by varying the path length of the antenna through selectable leg elements.

The antenna of this embodiment may be printed on various substrates, including paper-based materials such as labels, cards, and packages such as cardboard, or on non-paper materials such as glass or plastic. can. The antenna of the present invention can be printed using any conductive material, such as metal and carbon based inks. Carbon inks may contain structured carbon, such as graphene and carbon nanoonions, or a mixture thereof.

The characteristics of this embodiment include inherently flexible antenna technology and improved RFID range and flexibility. Applications of this antenna system include badges or clothing for telemetry of personnel, energy harvesting and communication such as groups, independent and numerous data telemetry and data acquisition, transportation processing without manual operation, Includes inventory management, including approval at the cargo handling port, location and internal content management, monitoring of fresh temperature, humidity, impact, etc., as well as energy harvested power supply or charging of internal products or connected circuits. Will be.

Although this embodiment is basically described with respect to a dipole antenna, the concept applies to any type of antenna, including array antennas and slot antennas. Slot antennas, typically used at frequencies between 300MHz and 24GHz, can be truncated from any surface to which this antenna will be mounted, and are largely omnidirectional (similar to a dipole antenna). It is common because it has a sexual radiation pattern. The polarization of the slot antenna is linear. The size and shape of the slot, and what lies behind this slot (cavity), give design variables that can be used to tune performance. One of the solutions to increase the directivity of the antenna is to use a reflector. For example, starting from a wire antenna (eg, a half-wave dipole antenna), a conductive sheet can be placed behind this antenna so that radiation is directed forward. Corner reflectors may be used to further improve directivity. Microstrip or patch antennas are becoming more and more useful because they can be printed directly on the circuit board.

Embodiments are essentially described with respect to energy harvesting, where the antenna is an energy harvester by absorbing energy. However, this concept also applies, but not limited to, the transmission and reception of all types of data, such as digital signals, analog signals, audio signals, and television signals.

Design factors for improving the reception of a two-dimensional (2D) flat antenna for conventional antenna radios are first described. One of the considerations in antenna design is antenna gain. Simply put, a higher gain antenna increases the power received from the antenna. High gain antenna designs are needed to ensure that the antenna has the longest reach (eg, 9 dBi and above). In short, the higher the gain, the higher the antenna range and vice versa. Another consideration is size and orientation. With respect to orientation, the optimum range from any antenna is achieved by ensuring that the antenna is fully oriented towards the source or properly oriented towards the source. As for size, a general rule of thumb is that smaller antennas have a shorter range and larger antennas have a longer range. Passive RFID antennas can vary in antenna range from a few inches to over 50 feet. Larger antennas generally have a larger antenna range, as larger antennas broadcast wider than smaller antennas.

As shown in FIGS. 1A and 1B, antenna polarization is another consideration in the design of 2D (flat) antennas. Polarization relates to the type of electromagnetic field generated by the antenna. The linearly polarized waves shown in FIG. 1A relate to radiation along a single plane. The circularly polarized wave shown in FIG. 1B relates to an antenna that divides the radiated power into two axes and thus "spins" the field to cover as many planes as possible. Absorption is improved when the antenna is aligned with the polarization of the source. Here, a linearly polarized antenna receives more than a circularly polarized antenna. Furthermore, with respect to the linear antenna, the field of the linear antenna extends farther than the field of the circular antenna in comparable gain, thus aligning with the antenna source, because the power is not split across more than one axis. If so, it is possible to make the antenna range longer. If the antenna is not aligned with the polarization of the source, the circularly polarized antenna will have a wider field of expansion than the linearly polarized antenna.

Resistance is yet another consideration in 2D antenna design, as increasing the resistance of the conductor reduces antenna reception. Printed antennas have been considered in the industry to achieve RFID technology that can be fully integrated into material manufacturing lines, such as package manufacturing. However, the drawback of printed antennas is that their radiation efficiency is lower than that of copper antennas because the bulk conductivity of the printed traces of the printed antenna is lower than that of solid metal. The main drawback of printed antennas is that they have limited conductivity compared to making antennas from solid metal. The basic rules for conductors and conductivity have shown that resistance loss decreases as the thickness of the conductor increases. Similar effects will apply to printed traces even if the printed ink traces are not uniform. An electrical transmission line printed at a given length and width and at a particular ink thickness has a total resistance that is proportional to the length and inversely proportional to the width and thickness of the trace. Resistance loss contributes significantly more to the loss of radiation efficiency than is caused by impedance mismatch. This is expressed by the following equation.

As the demand for telemetry increases and the characteristics of wireless electronic devices develop, more operating power is required. An improved, larger antenna is needed at the same cost as existing antennas.

Improvements in other aspects of energy harvesting, such as the ability to capture the various frequencies available in the surrounding environment, are also desirable for telemetry and IoT applications. Some conventional multi-band antenna systems utilize rectifier circuits to achieve impedance matching with the antenna. Other known antenna designs include multiple antennas, each antenna designed for a particular frequency. With this antenna, the circuit switches between different antennas. Another known type of antenna is a fractal ultra-wideband antenna that utilizes a fractal pattern. The fractal pattern allows multiple frequencies to be received simultaneously due to the various path lengths available in the fractal design. However, although these fractal antennas are wideband, the reception state of each of the individual frequencies of this antenna is weak because the signal current spreads at once over a plurality of frequencies.

Antenna with Frequency Selectivity Leg Element The antenna of this embodiment includes a single antenna in which the path length of the antenna can be changed so that the resonance frequency of the antenna can be adjusted. For example, the resonant frequency can be dynamically changed depending on which frequency has the strongest signal at that time in the surrounding environment. Therefore, this antenna can optimize the electric power in energy harvesting.

The antenna has a plurality of leg elements that form a continuous path. Here, one or more leg elements can be excluded. That is, it can be inactive during the operation of the antenna at the desired resonance frequency. Antennas collect energy only at specific resonant frequencies, for example, as opposed to fractal antennas that receive many frequencies simultaneously. Since only one frequency is picked up, the antenna operates with high efficiency. If it is desired to target a different frequency for energy harvesting, such as when the first signal being harvested is no longer available, but the strength of the second signal is increasing, then the antenna , Can be adjusted to have different antenna path lengths corresponding to the frequency of the second signal.

In general, the length of the antenna is set to correspond to the wavelength of the resonant frequency that the antenna is designed for. For example, a standard dipole antenna has two rods, each of which is one-fourth the wavelength of the target's resonant frequency. The overall length of the dipole antenna is half wavelength, which leads to a standing wave of rod voltage and current. A standing wave is when the current from the antenna feed point drops through the quarter wavelength antenna rod, is reflected from the end of the conductor (ie, the antenna rod), and returns to the feed point along the antenna rod. It is caused by the phase change of 360 degrees of the whole. The wavelength λ (meter) is related to the frequency f (MHz) by the following equation.

Therefore, the higher the received frequency, the shorter the length of the antenna. The present embodiment utilizes this principle for selectable antenna elements enabled by the printed leg elements.

2A and 2B are side sectional views of the antenna showing the concept of the frequency selectivity element. In FIGS. 2A and 2B, the antenna 200 has a plurality of leg elements 210, 220, and 230. The plurality of leg elements 210, 220, and 230 can both serve, for example, as one arm of a dipole antenna. Note that leg elements may also be referred to in this disclosure as leg segments. It is connected to a ground plane (not shown) at the end 201 to form a second arm of the dipole antenna. This end 201 is the end of the leg segment 210. The leg segment 210 has a length L ₁ , the leg segment 220 has a length L ₂ , and the leg segment 230 has a length L ₃ . The lengths L ₁ , L ₂ , and L ₃ are all illustrated as different from each other in this embodiment, but in other embodiments, may they all be the same? It may be a combination of the same length and different lengths. Further, although the antenna 200 is described as being linear, the antenna 200 may have any shape, such as, but not limited to, a curved shape, a spiral shape, or one having a bent portion with an inclination. There may be.

In FIG. 2A, all of the leg elements 210, 220, and 230 are active, so that the antenna path length is L _Aeff = L ₁ + L ₂ + L ₃ . In FIG. 2B, the element 230 is excluded, whereby the antenna path length is _{reduced to L Beff} = L ₁ + L ₂ , which is shorter than _{L Aeff.} Frequency relates equation 2, is inversely proportional to the _wavelength, since it is L _{Aeff> L Beff,} all elements are active, the antenna operating in mode of FIG. 2A, leg element 230 is not active, Resonates at a lower frequency than the same antenna in the mode of FIG. 2B. Therefore, FIGS. 2A and 2B show that changing the active length of the antenna arm by utilizing different combinations of one or more leg elements in the arm shifts the resonant frequency of the antenna. Is shown.

In any of the embodiments disclosed herein, this concept can be utilized in combination with the dimensional adjustment of antenna elements to further customize the frequency response. For example, the width of a leg element can be tapered along its length.

The present embodiment discloses an antenna system having a substrate and an antenna on the substrate. In this system, the antenna has multiple leg elements. The plurality of leg elements include conductive ink (ie, printed with conductive material) and form a continuous path. At least one of the plurality of leg elements can be individually selected or excluded to change the resonant frequency of the antenna, and the selected leg elements form the antenna path length corresponding to the resonant frequency. do. The resonance frequency may be changed by reducing the antenna path length due to the excluded leg elements being inactive in the plurality of leg elements. In some embodiments, the conductive ink is carbon-based and the substrate comprises paper. In some embodiments, the antenna is an energy harvester.

Frequency Selectivity Material Tuning In some embodiments, the leg element is selected or excluded by adjusting the material of the leg element. This affects the electrical impedance and thus the frequency response of the leg elements.

Impedance shows how difficult it is for alternating current to flow through an element. In this frequency domain, impedance is a complex number with a real part and an imaginary part due to the antenna acting as an inductor. Imaginary part is based on the frequency f and the inductance L of the antenna, an inductive reactance component X _L.

As the frequency received increases, so does the reactance, so that at a particular frequency threshold, this element is no longer active (when the impedance of the element is, for example, above 100 ohms). The inductance L is affected by the electrical impedance Z of the material. Here, Z is related to the material properties of the magnetic permeability μ and the dielectric constant ε due to the following relationship.

Therefore, the tuning of the material properties of the antenna, the electrical impedance Z changes, this affects the inductance L, and therefore, affect the reactance X _L.

This embodiment specifically confirms that leg elements with different inductances will have different frequency responses. That is, an antenna element with a high inductance L (based on electrical impedance Z) will reach a particular reactance at a lower frequency than another antenna element with a lower inductance. From Equation 3, the impedance is lower at lower frequencies (eg, 20 MHz to 100 GHz) than at higher frequencies. The leg element of the antenna, which has a lower impedance than the leg element of high impedance, becomes active and is utilized to increase the path length of the antenna to match the resonance for the desired frequency (with respect to Equation 2). As the frequency increases, the impedance of the element increases and becomes inactive at a particular resonant frequency threshold, i.e. ignored, effectively shortening the path length of the antenna and altering the resonant frequency. The selection or exclusion of leg elements based on frequency response is passive due to the properties of the material itself, without the need for electronic control. This novel concept of frequency selectivity material tuning is used to affect the optimum resonance tuning of the antenna by adjusting the antenna path length formed by the active element. In some embodiments, the response of the antenna can also be influenced by the conductivity σ of the antenna material.

This embodiment utilizes the properties of these materials, such as magnetic permeability, permittivity, and conductivity, to design each leg element with a particular electrical impedance to result in a threshold for a particular resonance frequency. do. In other words, tuning of the antenna material is used to form an ultra-wideband antenna element for maximizing energy harvesting and power transfer performance. The resulting "meta-antenna" has a range of frequencies from megahertz to gigahertz, as limited only by the physical limitation of the length of the antenna that can fit the substrate. On the other hand, it can be tuned well with a slight increase. By designing the frequency response of the leg element to the material of the antenna, the antenna has a unique leg element that can be passively selected or excluded. That is, an electronic circuit such as a microprocessor is not required to change the path length of the antenna. Instead, a particular leg element will be naturally turned on or off at the particular frequency for which this leg element is designed.

3A and 3B are side sectional views illustrating an embodiment of the use of material tuning for selecting or excluding leg elements of an antenna. Similar to the antenna 200 of FIGS. 2A and 2B, the antenna 300 of FIGS. 3A and 3B has a plurality of leg segments 310, 320, and 330. The leg segments 310, 320, and 330 can form one arm of the antenna, while the second arm (eg, the ground plane) is connected at the end 301 at the end of the leg segment 310. ing. The leg segment 310 has a length L ₁ and a magnetic permeability μ ₁ , the leg segment 320 has a length L ₂ and a magnetic permeability μ ₂ , and the leg segment 330 has a length L ₃ and a magnetic permeability μ ₃ have. The lengths L ₁ , L ₂ , and L ₃ are all illustrated as different from each other in this embodiment, but in other embodiments, may they all be the same? It may be a combination of the same length and different lengths. Further, although the antenna 300 is described as being linear, other shapes such as, but not limited to, a curved shape, a spiral shape, or an inclined shape can be used.

Permeability along the length of the antenna 300 has been screened so that μ ₁ is less than _{μ 2 and μ 2} is _{less than μ 3} away from the ground plane (at the end 301). And the magnetic permeability increases. Since the permeability is proportional to the inductance and thus the electrical impedance that affects the frequency response, the leg element 330, and thus the leg element 320, will be excluded as the frequency increases, and thus the antenna 300. Reduce the path length of. In other words, for each of the leg elements 320 and 330, there is a corresponding resonance frequency threshold. Above this threshold, the frequency response of the leg element 320 or 330 results in a non-conducting leg element 320 or 330 at a level sufficient to contribute to the antenna 300 with the leg element 320 or 330 active. .. Therefore, at a received frequency that is greater than the threshold of the resonant frequency of the leg element 330 but less than the threshold of the resonant frequency of the leg element 320, the leg element 330 has a resulting level of impedance. Excluded by being inactive due to the high, the leg element 320 is selected by being activated due to the resulting low impedance. Further, if the received frequency is at a higher level above the threshold of the resonant frequency of the leg element 320, the leg element 320 will also be inactive due to the high level of impedance resulting. It will be excluded by that.

For example, in FIG. 3A, the received frequency of the EM signal is low enough with respect to the resulting impedance of all of the leg elements 310, 320, and 330 being low enough, thereby the leg element 310. , 320, and 330 are all active. That is, the received frequency in FIG. 3A is less than the threshold of the resonant frequency of the leg elements 310, 320, and 330. Therefore, the path length of the antenna is L _Aeff = L ₁ + L ₂ + L ₃ , and the antenna has a resonance frequency corresponding to a _{quarter wavelength L Aff.} FIG. 3B shows that the received frequency is higher than that of FIG. 3A and the resulting impedance of the leg element 330 is high enough so that the leg element is too high to contribute to the antenna 300. It shows the situation. Therefore, in FIG. 3B, the leg element 330 is not active, where the received frequency is higher than the threshold of the resonance frequency of the leg element 330. The antenna path length is reduced only to _{L Beff} = L ₁ + L _2, which is shorter than _{L Aeff.} The antenna of FIG. 3B will have a higher resonance frequency than the antenna of FIG. 3A.

3A and 3B show an embodiment of an antenna in which the first leg element of the plurality of leg elements has a threshold of the first resonant frequency depending on the received frequency. The first leg element is passively excluded from the antenna path length by making it inactive when the received frequency is greater than the threshold of the first frequency. In some embodiments, the second leg element of the plurality of leg elements has a second resonance frequency threshold that depends on the received frequency, and the second resonance frequency threshold is the first. The second leg element is passively selected by resonance if the received frequency is less than the threshold of the second resonance frequency. The second leg element can be passively excluded in addition to the first leg element if the received frequency is greater than the threshold of the second resonant frequency, reducing the antenna path length. In some embodiments, the first resonant frequency threshold is based on the first electrical impedance of the first leg element, and the second resonant frequency threshold is the second electrical of the second leg element. Based on the target impedance. The second electrical impedance is different from the first electrical impedance due to the difference in material properties. Material properties are selected from the group consisting of magnetic permeability, dielectric constant, and conductivity.

In some embodiments, the antenna system comprises a substrate and an antenna on the substrate. The antenna has a plurality of leg elements, which are provided with conductive ink and form a continuous path. The first leg element of the plurality of leg elements has a first resonance frequency threshold that depends on the received frequency and the first electrical impedance of the first leg element. The first electrical impedance is based on material properties selected from the group consisting of magnetic permeability, dielectric constant, and conductivity. The first leg element can be individually excluded so as to change the resonant frequency of the antenna by changing the antenna path length. The first leg element is passively excluded from the antenna path length by making it inactive when the received frequency is greater than the threshold of the first frequency. In certain embodiments, the second leg element of the plurality of leg elements has a threshold for the received frequency and a second resonant frequency that depends on the second electrical impedance of the second leg element. The second resonance frequency threshold is higher than the first resonance frequency threshold due to the difference in material properties compared to the first leg element. The second leg element is passively selected by resonance if the received frequency is less than the threshold of the second resonance frequency.

FIG. 4 shows a perspective view of the antenna 400, which implements the material tuning concept of a standard flat inverted F antenna (PIFA) design. An embodiment of the antenna 400 has a ground plane 405 and a plurality of leg elements 401 that are segments of the antenna 400. The leg element 401 includes a first leg element 410 and a second leg element 420. The first leg element 410 has a magnetic permeability μ ₁ and the second leg segment 420 has a magnetic permeability μ ₂ and μ ₁ > μ ₂ . The leg element 410 is not available at high received frequencies above its resonant frequency threshold, as indicated by the dashed box 415. The reason for this is that the impedance of the leg element 410 becomes too high. In other words, at a sufficiently high frequency, the leg element 410 does not respond and the current is reflected at the intersection between the leg element 410 and the leg element 420. Therefore, the antenna path length along the "F" shaped path is shortened and the resonance frequency is increased. At higher frequencies, the leg element 420 is also unavailable because the impedance becomes too high, which further reduces the length of the antenna path along the current flow. .. That is, the dashed boxes 415 and 425 areas are excluded to increase the resonant frequency.

The ability to change material properties along the length of the antenna is uniquely made possible by printing the antenna. Printing can be performed, for example, by inkjet printing, flexographic printing, or silk screen printing. In some embodiments, the conductivity of the material varies along the antenna. In embodiments where carbon-based inks are used, the type of carbon allotrope (eg graphene, carbon nanoonions, etc.) can be varied between leg elements or the conductivity of the allotrope can be varied (eg,). , Low density graphene has lower conductivity than denser graphene). In some embodiments, the permeability of the material can be varied to affect the frequency threshold of the leg element. For example, ferromagnetic materials (eg, iron oxide) can be used at low frequencies (eg, 500 kHz to 500 MHZ), and paramagnetic materials (eg, iron silicide) can be used at high frequencies (eg, 500 kHz to 5 GHz). Can be used in, or antiferromagnetic materials can be used. In some embodiments, the permittivity can be tuned to achieve the desired impedance value of the leg element, either alone or in combination with conductivity and permeability.

Conventional antenna elements are usually made of a single type of material, the associated conductivity of which affects a particular resonant frequency. In contrast, the antenna material of this embodiment is printed. Here, the print ink can be customized by variable characteristics within a single antenna subsection to affect its resonant frequency by varying the path length of the antenna that is active with respect to the resonant frequency. Customization of material properties can be achieved by changing the magnetic permeability, dielectric constant, and / or conductivity of the legs. This adjustment of antenna material may eliminate further changes to the antenna and / or matching network elements in cases where energy reception and transmission are improved.

Frequency Selectivity Digital Tuning In addition to changing the path length by tuning the antenna material to respond to different frequencies, in some embodiments the path length of the antenna is electronically selected or excluded from the leg elements. Can be changed by FIG. 5 shows an antenna 500 with a PIFA design similar to FIG. Here, the antenna 500 has a ground plane 505 that serves as one antenna arm and a plurality of leg elements 501 that serve as a second antenna arm. The plurality of leg elements 501 include a first leg element 510, a second leg element 520, and a third leg element 530. The leg elements 510, 520, and 530 include gaps between the leg elements, such as a gap 560 between the leg element 510 and the leg element 520, and a gap 561 between the leg element 520 and the leg element 530. Parallel segments that form a meandering pattern. The electrical connections 515, 525, and 535 are connected to the respective ends of the leg elements 510, 520, and 530 at the intersections between the leg elements. The electrical connections 515, 525, and 535 are electrical leads that are electrically coupled to an electronic circuit 550, such as a microprocessor. The electronic circuit 550 described in the "Tuning Circuits" section of the present disclosure may short-circuit the leg elements together to exclude these leg elements. For example, the connections 515 and 525 can be bridged by an electronic circuit such that the leg element 510 is shorted to the leg element 520 and the presence of the leg element 510 is efficiently removed (ie, excluded). ..

6A-6C show how leg elements can be excluded so as to change the frequency at which the antenna 500 resonates. Graphs of S-parameters (S1,1) are shown for various combinations of leg elements. In FIG. 6A, the entire antenna 500 is used. Here, all leg elements 501 are selected and active. The resonance frequency is 2.42 GHz in FIG. 6A. In FIG. 6B, the leg element 510 is functionally removed, as indicated by the blank area 517. This exclusion of the leg element 510 is achieved by bridging the connection 515 and the connection 525 together using an electronic circuit 550, thus shorting the leg element 510 with respect to the leg element 520. In FIG. 6B, the resulting antenna path length is shorter than the entire antenna of FIG. 6A, thus the central frequency is higher and shifts to 2.475 GHz. In FIG. 6C, both the leg element 510 and the leg element 520 are removed, as indicated by the blank area 517 and the blank area 527. The leg elements 510 and 520 are excluded by bridging the connections 515, 525, and 535 together, thus shorting the leg elements 510, 520, and 530 to each other. Although the antenna path length in FIG. 6C is even shorter than in FIG. 6A or FIG. 6B, the frequency does not increase as expected, but shifts low to 2.34 GHz. The reason for this is that the capacitance is reduced due to the elimination of parallel leg elements in the F-shape design (eg, elimination of the effect of capacitance due to the gaps 560 and 561). Thus, the geometry of the entire antenna (eg, meandering, spiraling, linear) can be used in combination with selectable leg elements to adjust the antenna for the desired resonant frequency. It can be seen that the effect of capacity can occur.

5 and 6A-6C show an embodiment in which the antenna system has an electronic circuit having connections to each of the plurality of leg elements. The electronic circuit is to dynamically exclude the first leg element among the plurality of leg elements by short-circuiting the first leg element among the plurality of leg elements with respect to the second leg element. It is configured.

In some embodiments, the energy harvesting system includes an antenna system and an electronic circuit. The antenna system includes a substrate and an antenna on the substrate. The antenna has a plurality of leg elements, the plurality of leg elements including carbon-based conductive ink and forming a continuous path. Each of the plurality of leg elements can be individually selected or excluded so as to change the resonant frequency of the antenna, and the selected leg elements form an antenna path length corresponding to the resonant frequency. The electronic circuit has a connection to each of the plurality of leg elements, wherein the electronic circuit short-circuits the first leg element of the plurality of leg elements with respect to the second leg element. Is configured to dynamically exclude the first leg element from the plurality of leg elements.

In some embodiments, the electronic circuit identifies a plurality of available frequencies in the surrounding environment and sets the resonant frequency based on the power level of the plurality of available frequencies. It includes a switching circuit communicating with the connection, which adjusts the antenna path length to correspond to the resonant frequency by selecting or excluding the leg element from the leg elements of. In certain embodiments, the identification circuit comprises a microprocessor that sets the resonant frequency to be the frequency with the highest power level of the plurality of available frequencies.

In some embodiments, material tuning embodiments and electronic switching embodiments can be used in combination. For example, leg elements with different magnetic permeability of FIG. 4 can also have the electrical lead connection of FIG. Matching each method can lead to further customization of the changes in the resonant frequency response that can be performed. This is shown, for example, by graph 700 of the S-parameters of FIG. This curve shows the response of S (1,1) for linear antennas of various lengths. Here, curve 710 indicates a unit length of 1, curve 720 relates to a unit length of 2, curve 730 relates to a unit length of 3, and curve 740 relates to a unit length of 3. The curve 750 relates to a unit length of 0.5. As can be seen, the peaks of the resonant frequency shift relative to each other due to the different antenna lengths. Curve 715 demonstrates the use of material tuning in combination with electrical switching for one resonant peak of curve 710. That is, the narrow resonant peak of the curve 710 is widened when the digital tuning is combined with the material tuning. In other words, the antenna length formed by electronically excluding the elements will still lead to specific resonant frequency responses, but when material tuning is used together, around these resonant frequencies. With a wider band response. As can be seen, the antenna can serve as a resonator constructed to operate at a particular frequency, including a resonant frequency range around a particular frequency.

Capacitance Tuning In a further embodiment, the dielectric material can be printed within the structure and / or substrate of the antenna to change the capacitance of the antenna. For example, a printed dielectric element can be used between two leg elements within a plurality of leg elements. This capacitance tuning concept is illustrated by the microstrip antenna 800 shown in FIGS. 8A and 8B. Here, FIG. 8A is a plan view, and FIG. 8B is a side sectional view. The patch antenna 810 is powered by the microstrip transmission line 820, and both the patch antenna 810 and the microstrip transmission line 820 are mounted on the surface of the substrate 830. The ground plane 840 is attached to the opposite side of the substrate 830. The patch antenna 810, the microstrip transmission line 820, and the ground plane 840 are made of a highly conductive metal (usually copper in conventional antennas). The patch antenna 810 has dimensions of a length L and a width W. The substrate 830 is a dielectric circuit board having a dielectric constant of ε _r and having a thickness of h.

The thickness of the ground plane 840, or the microstrip formed by the antenna 810 and the transmission line 820, is not critical. Normally, the height h is well below the working wavelength, but should not be much shorter than 0.025 (1/40 of the wavelength) of the wavelength, otherwise the efficiency of the antenna will be reduced. It will be.

The operating frequency of the patch antenna 810 is determined by the length L. The center frequency f _c (ie, the resonant frequency) is approximately given by:

Thus, the resonance frequency of the antenna 800 is affected by the dielectric constant of the substrate 830. In the embodiment of FIG. 8B, the dielectric layer 850 can be printed on the front surface (and / or back surface) of the substrate 830 so as to change the collective dielectric constant of the substrate 830. In other embodiments, the substrate 830 may be layered, such as in a corrugated board structure, where the dielectric element is on any of the outer surfaces of the cardboard and / or in an intermediate layer of the cardboard ( For example, it can be printed on a wavy layer). The use of printed dielectrics allows for good tuning of material properties and dimensions to uniquely adjust the capacitance and, ultimately, the frequency response of the antenna.

In some embodiments, the printed dielectric element is available between the leg elements to customize the frequency response of the antenna. For example, returning to FIG. 5, the gap 560 and / or the gap 561 can be formed using the printed dielectric ink. The properties of the ink can be customized to form a particular capacitance between the leg elements. The dimensions of the printed dielectric can also be controlled by the printing process.

2D Antennas on Substrate An example of antenna design is provided here. In this antenna design, the above-mentioned frequency selectivity characteristics can be implemented together with the printed antenna on the substrate. A flat (2D) antenna is described first.

FIG. 9 shows the antenna 900 configured as the PIFA design described above with respect to FIGS. 4 and 5. The PIFA antenna 900 has an F-shaped antenna 901 that serves as one conductor and a ground plane 905 that serves as another conductor in this dipole design. An exemplary antenna gain response 910 (dBi) for the antenna 900 is modeled at a Bluetooth® frequency of 2.443 GHz and exhibits a uniform radiation pattern in all directions. In other words, the antenna gain response 910 has a receive or transmit directivity that allows the antenna 900 to emit or receive from substantially any direction.

FIG. 10 shows a wavy antenna 1000 having two identical pairs of orthogonal flat arms 1001 and arms 1002. Each of the arms 1001 and 1002 has selectable leg elements as described in the material tuning embodiments, electronically switchable embodiments, and / or capacitive tuning embodiments of the present disclosure. Can be configured. Each edge of the arms 1001 and 1002 is a wavy curve swinging back and forth across the bisector 1005 of the angular sector angular sector θ in the circumferential direction. Each of the arms 1001 and 1002 is an alternating sequence of geometrically similar cells on one side of the bisector 1005. The sector angle θ can reach 180 degrees or more, so that cells of adjacent arms are inserted but not in contact. The learning shape of each arm is completely identified by two angles, a log-periodic growth constant, and an inner radius and an outer radius (DuHamel, and known techniques by Filipovic & Cencich). ). High performance wavy antennas are usually self-complementary and are tightly wound to achieve a stable radiation pattern and impedance over the operating frequency band. Response 1010 and response 1020 are shown in two designs. An antenna with a resonant frequency of 2.75 GHz is shown in response 1010 and a resonant frequency of 5 GHz is shown in response 1020.

11A-11C show a flat antenna 1110 printed on two adjacent sides 1122 and 1124 of an object 1120, such as a transport box. The two antenna arms 1101 and the antenna arm 1105 (ie, conductor) of the antenna 1110 may be, for example, a ground plane and F-shaped element of the PIFA design. 11B and 11C show that the length of element 1101 can be varied with respect to the desired resonant frequency (as in the graph of FIG. 7), in this embodiment of the antenna element (arm) 1001. The path length is shorter in FIG. 11B than in FIG. 11C. The change in antenna path length may be achieved by excluding the leg element within the antenna arm 1101.

Although the geometries of PIFAs and wavy antennas are known, FIGS. 9 and 10 show that the frequency selective antenna design of this embodiment can be applied to a wide variety of geometries, from simple to complex. Is shown. Since this antenna is printed, it is possible to achieve a more complicated geometric shape than a general antenna. 11A to 11C show that the antennas of the present disclosure can be configured in a 3D fashion, such as those for improving polarization.

3D antenna on board This frequency selective printed antenna has a 3D structure by incorporating the antenna components as an intermediate layer on the board for electrically active layering on the surface and reception of electromagnetic fields. It can also be carried out as. In order to improve the reception of general antennas, the size, number, and dimensions of the antennas have been improved in this embodiment. While some embodiments herein describe substrates for packaging, such as corrugated cardboard, other types of multi-layer substrates, including paper, glass, and plastic, are also included within the scope of this disclosure.

In some embodiments, the substrate material itself is a 2D or 3D energy device. It is a true 2D / 3D energy harvester, not just an antenna printed on the outside of the board, as in conventional antennas. The frequency selective antenna technology of the present disclosure is incorporated within a layer of a multilayer material and includes a type of packaging such as a cardboard box. The antenna technology utilizes conductive and dielectric materials for RF reception purposes for remote measurement and energy harvesting to power RFID and advanced electronics. Antennas can be used for energy harvesting or communication, or for other suitable or available electromagnetic energy sources, such as providing RF energy harvesting capabilities for 915 MHz or 2.45 GHz.

It is known that the 3D feature can be added to the 2D antenna by bending the antenna component or the like to improve the reception of the antenna. However, bent materials typically result in higher losses due to the reduced resistance value due to changes in the input impedance of the antenna when distorted by bending.

In this embodiment, the reduction of resistance in the bent antenna material is suppressed, thereby providing a 3D effect that can be adjusted to improve the impedance of the entire matching antenna by bending the structure. The overall performance is improved. By using a layer of 3D structure such as cardboard as a conductor and a dielectric to form a resonant cavity, it enables not only high reception performance but also multiple frequencies. With the resulting improvement in performance via the 3D structure, resistance limitations can be relaxed in the design of the structure.

FIG. 12A shows a perspective view of a folded inverted-F antenna 1200 (FIFA), but is implemented as a 3D structure that can be incorporated into a substrate. FIG. 12B is a partial side sectional view. The antenna arm 1210 is a radiating element that can be configured with the frequency selectivity element as described above. The antenna arm 1210 is formed from a top metal coating layer 1212 on a first layer 1231 of the substrate 1230 and a bottom metal coating layer 1214 (for clarity, the substrate 1230 is not shown in FIG. 12A. Please note). Slot 1216 is etched from both the metal coating layer 1212 and the metal coating layer 1214, separating the antenna arm 1210 into subpatches 1218. Two slots 1216 each of layers 1212 and 1214 forming the three subpatches 1218 are shown in FIG. 12B for simplicity, but other configurations are possible (eg, five subpatches, Or any suitable number of subpatches). A via 1219 connects the metal coating layer 1212 and the metal coating layer 1214. For proper operation of the antenna, the antenna arm 1210 is provided at a specific height above the ground plane 1240, is supported by feed pins 1280 and short circuit pins 1290, and is a top metal coating layer of the radiating antenna element 1210. The 1212 and the bottom metal coating layer 1214 are connected and connected to the ground plane 1240 below. The ground plane 1240, which is shown in FIG. 12B on the inner surface of the second layer 1232 of the substrate 1230, shall be on the outer surface (ie, the outer surface of the second layer 1232). You can also. During operation, the lead wire 1285 provides an electrical connection to the supply pin 1280 so that it collects the output signal from the antenna 1200.

In FIG. 12B, the substrate 1230 is a 3D structure implemented as a wavy intermediate. For example, the first layer 1231 can be the first linear board, the second layer 1232 can be the second linear board laminated on the first layer 1231, and the first. There is an intermediate layer 1233 in the gap G between the layer 1231 and the second layer 1232. Intermediate layer 1233 is shown in this embodiment as a wavy layer with flutes. In the design of the substrate 1230, the gap G can be customized according to the desired height between the antenna arm 1210 and the ground plane 1240. In a further embodiment, the printed dielectric component is the collective capacitance of the antenna 1200, such as on any layer of the first layer 1231, the second layer 1232, and the intermediate layer 1233 within the gap G. It can be inserted into the gap G so as to adjust the capacitance. In some embodiments, each part of intermediate layer 1233 can be printed with a conductive material so that it can be electrically connected to an electronic circuit so as to select and exclude leg elements. Examples of these printed conductive elements 1235a and 1235b are shown on each of the upper and lower surfaces of the intermediate layer 1233.

In some embodiments, the ground plane 1240 can be used as a shield element. For example, if the substrate 1230 is corrugated cardboard formed into a shipping container, the substrate 1230 can be oriented such that the second linear board 1232 is on the outside of the box. Any part of the container having a ground plane 1240 covering the second linear board 1232 will have an electromagnetic shield for the contents inside the container. The ground plane 1240 may be on the inner surface of the second linear board 1232 as shown in FIG. 12B or on the outer surface of the second linear board 1232 (outside the second linear board 1232). Please note.

FIG. 13 is a perspective view of a dual-band flat inverted-F antenna (PIFA) 1300 in the L slot. The antenna 1300 includes a rectangular flat element that serves as an antenna arm 1310, a ground plane 1340, a supply pin 1380, and a short circuit plate 1390. The short circuit plate 1390 is illustrated in FIG. 13 as a plurality of short circuit pins. The short circuit plate 1390 between the flat element (antenna arm 1310) and the ground plane 1340 is usually narrower than the side of the flat element to be shorted. The L-slot PIFA-style antenna arm 1310 can have a frequency selectivity leg element incorporated therein to allow the antenna 1300 to have an adjustable resonant frequency. The antenna 1300 can also be incorporated into a 3D substrate in a manner similar to that described with respect to FIGS. 12A and 12B. FIG. 13 also shows the antenna gain response 1303. In the antenna gain response 1303, the antenna 1300 radiates uniformly in the radial direction in a plane parallel to the ground plate 1340.

FIG. 14 is a printed perspective view of the bent inverted F antenna 1400. Antenna 1400 has an etched metal wire on a dielectric 1430, forming a bent inverted F shaped antenna arm 1410. The outer fork of F is short-circuited by the supply pin 1480 to the edge of the ground plane (not seen in this figure) located on the rear surface of the dielectric 1430. The ground plane covers a section of the dielectric, i.e., a section that does not come directly under the bent inverted F arm 1410. The antenna arm 1410 is supplied by the supply pin 1480 at the second fork with respect to the edge of the ground plane. The bent inverted F style antenna arm 1410 can have a frequency selectivity leg element incorporated therein to allow the antenna 1400 to have an adjustable resonant frequency. Antenna 1400 can also be incorporated into a 3D substrate in a manner similar to that described with respect to FIGS. 12A and 12B. FIG. 14 also shows the antenna gain response 1403. In the antenna gain response 1403, the antenna 1400 radiates uniformly in the radial direction in a plane parallel to the ground plate 1340.

FIG. 15 shows a perspective view of another flat inverted F antenna 1500. In this figure, this PIFA style is yet another embodiment of the design, in which the selectivity leg element can be incorporated as a 3D structure. The antenna 1500 typically includes an antenna arm 1510, a ground plane 1540, and a rectangular flat element that acts as a short circuit plate 1590 with a width narrower than the width of the shorted side of the flat element. There is. Supply pins 1580 are also shown and serve as supply points for frequency signals received by antenna 1500. The antenna gain response 1503a is shown in graph 1503b, which is a plot of the corresponding S (1,1) responses.

FIG. 16 is a perspective view of a rectangular, electromagnetically coupled patch antenna 1600. The EM-coupled patch antenna 1600 has an electromagnetically coupled patch element 1610 and a supply line 1680. The patch element 1610 is located on top of the upper dielectric 1631 of the two dielectric substrates 1630. The two dielectric substrates 1630 also include a lower dielectric 1632. The supply line 1680 is between the upper dielectric substrate 1631 and the lower dielectric substrate 1632 and extends under the patch 1610. Bandwidth is improved by having the patch element 1610 on top of a thick substrate 1630 (two dielectric structures thicker than a single layer), while spurious radiation is located near the ground plane 1640. Limited by having a supply line 1680. The ground plane 1640 is on the rear surface of the dielectric 1632. The frequency selectivity leg element can be incorporated into the patch element 1610 and the entire antenna 1600 can be constructed as a 3D structure incorporated into the substrate material. Antenna gain response 1603 is also shown.

12A / 12B to 16 are examples of known types of antennas that can incorporate the selectivity leg elements of the present disclosure as a 3D structure. In some embodiments, the 3D structure can be implemented on a multi-layered substrate, such as a wavy intermediate. Examples of wavy structures that may be used include a single face, a single wall, two walls, and three walls. A single layer, two layers, or even more layers can be added to result in a high receive antenna system. Layers individually deposited on the components of the substrate can be laminated or adhered to the final structure. In some embodiments, the adhesive used to bond the substrate layers together is also by changing the collective capacitance of the antenna, such as by using a printed dielectric in the intermediate layer. It can be used to adjust the frequency response of the antenna.

In some embodiments, such as those shown by FIG. 12B, the substrate for the antenna comprises a first layer, a second layer laminated on the first layer, and a first layer. It includes an intermediate layer in the gap between it and the second layer. The plurality of leg elements are on the first layer, and the plurality of leg elements form the first antenna arm of the antenna. The antenna further comprises a second antenna arm on the second layer (eg, a ground plane for a dipole antenna) and a conductor on the intermediate layer (eg, conductive elements 1235a and 1235b), wherein the conductor is , The second antenna arm is electrically coupled to a plurality of leg elements. In certain embodiments, the multilayer substrate can be cardboard and the intermediate layer is a wavy intermediate. In some embodiments, the gap between the first and second layers of the substrate serves as a dielectric between the first antenna arm and the second antenna arm. In some embodiments, the clearance characteristics can be customized to affect the action of the antenna. For example, the distance of the gap and the characteristics of the material in the gap (eg air, substrate material for the intermediate layer, and the dielectric inserted in the gap) are affected by the capacitance of the antenna and thus the capacitance of the antenna. The frequency response of the antenna can be changed.

Various types of 3D features, such as flute configurations (wave patterns in the xy plane extending in the z direction perpendicular to the wave plane) found in common wavy intermediates, are used in the substrate. Can be done. However, other 3D features such as waves in the x, y, and z directions, or various types of wave patterns are possible. In general, the 3D feature used in the embodiments of the present disclosure is to have a curved transition because the sharp edges create discontinuities in the electrical path within the antenna. In some embodiments, the 3D features of the substrate can also be designed to contribute to the resonant frequency of the antenna. For example, if the intermediate layer has electrical conduction wires printed on it so that it acts as an electrical connection to the switching circuit, the wave period is expected to be captured or transmitted. It can be designed according to the resonance frequency that is being used.

Using the packaging material as an example, it is possible to significantly increase the functionality associated with energy harvesting by incorporating the antenna into a packaging container. ^{As a sample configuration, for a small box with 1ft 2} sides with antenna material incorporated in 80% of the area, the packaging container is 0.5mA to 1mA at about 2.6V. Can be provided in size. By using the storage device like a low-cost supercapacitor, this amount of current can power significantly more functions (including memory) than conventional energy harvesting devices. An embodiment of the improved functionality application is to record the temperature of the package during transport.

Manufacture of 3D Printed Antenna Figure 17 is a schematic of an exemplary process for manufacturing a printed, frequency-selective antenna. The schematic of FIG. 17 shows the packaging material for a 3D antenna, but this process also applies to 2D (eg, single layer) substrates. FIG. 18 is a corresponding flowchart. In some embodiments of FIGS. 17 and 18, the energy harvesting device comprises a printed packaging material and the electrically conductive material is printed on a packaging material sheet. The printed packaging material is formed in a packaging container.

In the embodiment of FIG. 17, the substrate material is a card stock 1720, and the antenna material is printed on the card stock 1720 by using a multi-jet fusion process 1710 or the like. In the embodiment of FIG. 17, the printed cardstock is wavy and layers of the final structure are assembled in process 1730, such as by gluing. The process 1730 shows a first liner 1731, a wavy roller 1732, an adhesive coating machine 1733, a pressure roller 1734, a heater roller 1735, and a second liner 1736. The first liner 1731 corresponds to the intermediate layer 1233 of FIG. 12B, and the second liner 1736 can be the first layer 1231 or the second layer 1232 of FIG. 12B. Another liner (not shown) is added to form the other liner in FIG. 12B (second layer 1232 or first layer 1231).

In a schematic embodiment, the printed packaging material can include multiple layers, where the assembled layers are dimensions that affect the resonant frequency of the antenna, such as by forming resonant cavities. And can have material properties. The resulting packaging 1740 is a 3D energy harvesting device (or transmit and / or receive device), such as the corrugated cardboard container shown in FIG. In various embodiments, flat antennas can be used due to the availability of larger areas, or multi-layer (3D) devices can be used depending on the application. ..

In some embodiments, the substrate on which the antenna is printed is flexible in its natural state at room temperature, such as a paper-based or plastic-based substrate in the form of a sheet or film. In some embodiments, the substrate can be formed into the desired 3D learning shape in one condition, such as in a heated state with respect to a glass or plastic material, but the substrate becomes stiff at room temperature. , Inflexible. In various embodiments,
The substrate can be a disposable and / or biodegradable, low cost material for use in applications such as packaging, labels, tickets, and identification cards. Paper or plastic substrates can be particularly useful in these low cost applications.

FIG. 18 is a flowchart 1800 of an exemplary method for manufacturing a selectivity antenna system, which can be, for example, an energy harvesting system. In step 1810, a substrate is provided. The substrate can be a single layer material or a multi-layer material with a 3D structure. Step 1820 comprises printing the antenna onto a substrate using conductive ink, the antenna comprising a plurality of leg elements forming a continuous path. Each of the plurality of leg elements can be individually selected or excluded so as to change the resonant frequency of the antenna, and the selected leg elements form an antenna path length corresponding to the resonant frequency. The antenna can be a flat antenna printed on a single surface of the substrate material, or it can be a 3D structure with various antenna components incorporated within a layer of the substrate. Selectable / excludeable leg elements are material tuned (eg, the type of conductive material used in the ink and / or adjustment of material properties such as permeability, dielectric constant, and conductivity), electronically switched. Possible connections, printed dielectric elements, leg element dimensions (eg, tapered widths), or any combination thereof can be used to adjust for various resonant frequency thresholds. Printing in 1820 can include, in some embodiments, printing a dielectric component using a dielectric ink.

For embodiments where the leg elements are dynamically selectable / exclude, in step 1830 an electronic circuit is coupled to the antenna. The electronic circuit has a connection to the leg element of the antenna, whereby the leg element can be controlled individually. The electronic circuit can search for available frequencies in the surrounding environment and analyze the power level of each frequency. In some embodiments, the electronic circuit may select the target resonant frequency based on which frequency is the most powerful source of power. In other embodiments, the electronic circuit may select a targeted resonant frequency according to a characterized wavelength so that it can be received by the user or device associated with the electronic circuit and antenna. In embodiments where the antenna is an energy harvesting antenna, the method also includes step 1840, which involves coupling an energy storage component to the antenna. The energy storage component stores the energy received by the antenna and can also be, for example, a battery or a capacitor. At step 1850, the device is coupled to an energy storage component, which allows the device to be powered by the energy harvested by the antenna.

Print Inks Various types of inks, including customary silver or carbon inks, can be used to print the antenna system of the present invention. In some embodiments, the ink for printing the antenna can be a mixture of carbon (eg, graphene) and metal to obtain high conductivity. In some embodiments, the antenna is made of printable conductive carbon, including characteristic carbon materials formed by novel microwave plasma and pyrolysis equipment and methods, and composites of carbon materials. It is formed. This carbon material was disclosed, for example, in US Pat. No. 9,862,606, entitled "Carbon Allotropes," and US Patent Application No. 15 / 711,620, entitled "Seedless Particles with Carbon Allotropes." For example, carbon material. Both of these documents are owned by the applicant of this application and are incorporated herein by reference in their entirety. The types of carbon materials for the various embodiments of the printed components are, but are not limited to, multi-layer fullerenes, graphene, graphene oxide, sulfur-based carbon (eg, carbon in which sulfur is dissolved and scattered), and metals. Includes carbon (eg, carbon infused with nickel, carbon with silver nanoparticles, graphene with metal). Mixtures of carbon with a well-defined structure, such as graphene and / or carbon nanoonions, can also be used. Two or more types of carbon can be used for the leg element of the antenna to tune the material properties and thus the threshold of the resonant frequency of each leg element.

In some embodiments, the ink comprises a tunable, multi-layered spherical fullerene, and a hybrid form thereof, wherein the fullerene is a parameter of the decomposition process used to provide this fullerene (eg, thermal decomposition). Or it has a physical structure that can be tuned by (microwave decomposition). Conventional carbon inks can be highly conductive, but some conventional materials are unique and necessary to truly provide a printable device with high gain, low cost. Capacitance and dielectric properties are lacking. In addition, the high levels of impurities commonly found in these materials are 1) dynamically controlling and tuning the inherent frequencies of the transmission and reception of signal RF and power RF, and 2) single or multiple. Allows the ability to dynamically direct RF energy in the desired direction (s) towards the device, and 3) communication between two or more devices and transmission of power. To support both, prevent continuous doping or incorporation with other materials in order to improve the overall gain to a substantial level. In this embodiment, the tunable carbon can be effectively printed on a wide variety of suitable substrates while being incorporated into a wide variety of applicable ink compositions and overcoming these obstacles. Can provide the performance required to do so. These carbon materials and antennas can also support a variety of functions. Utilizing simultaneous or combined transmission and reception of various forms of RF for energy harvesting, signal transmission, or both, using switching elements and / or primary modulation. Can be done. With the help of control hardware, these antennas can support the actual harvesting of base carrier or sideband frequency energy, in addition to signal decryption.

In some embodiments, the printable ink is transparent, such as for use within a layer of material on a visual display component.

In some embodiments, the dielectric ink may be used to print the dielectric element in the antenna system, as described above in the present disclosure. Examples of dielectric materials for dielectric inks include, but are not limited to, inorganic dielectrics (eg, aluminum oxide, tantalum oxide, and titanium dioxide), and polymer dielectrics (eg, polytetrafluoroethylene (PTFE)). ), High Density Polyethylene (HDPE), and Polycarbonate).

In some embodiments, the magnetic dielectric (MD) ink can be used in the present antenna system to form the antenna element. Magnetic dielectric ink can also be used to form a layer between the substrate and the printed antenna, allowing for improved antenna efficiency and miniaturization of the antenna, as well as any type of substrate for the antenna. Serves as a decoupling material so that it can operate on. Antenna miniaturization techniques in materials are based on the influence of the material's electromagnetic parameters on antenna size. The electrical wavelength λ is inversely proportional to the value of the refractive index as follows.

In equation 6, c is the speed of light and _fr is the resonance frequency of the antenna. Equation 7 states that each of the permittivity ε and the magnetic permeability μ has a real part (ε'and μ') and an imaginary part (ε'' and μ''), and the imaginary part relates to frequency. Shows. As can be seen in Equation 6, the properties of the material can be used to determine the size of the antenna for a given resonant frequency. By convention, high dielectric constant materials for antenna substrates or super straights are used for antenna miniaturization. However, increasing the relative permittivity of the substrate material has the disadvantages of narrow bandwidth and low efficiency. These drawbacks come from the fact that the electric field remains in the high dielectric constant region and is not diverged. Low characteristic impedances in media with high dielectric constants also lead to impedance matching problems.

In contrast, MD materials with greater than 1 ε _r and μ _r can reduce antenna size with better antenna performance than antennas on high dielectric constant materials. Known studies have shown that adequately increasing relative permeability leads to an efficient reduction in the size of microstrip antennas. Impedance bandwidth can be maintained after miniaturization. By using the cavity model, the radiation efficiency and bandwidth of the patch antenna placed on the lossy MD material has shown that these MD materials are effective in reducing the antenna size. From this technique, relative permittivity has a negative effect on radiation efficiency and bandwidth, while relative permeability has a positive effect on both radiation efficiency and bandwidth. It has been shown that various antenna designs of MD materials can reduce antenna size without compromising antenna radiation efficiency and bandwidth. The present embodiment can further apply the use of magnetic dielectric materials to antenna design by uniquely tuning the material properties of magnetic permeability and dielectric constant for a particular configuration. For example, MD material properties can be tuned to have a particular resonant frequency with respect to the antenna leg element, or to make the MD element a decoupling layer between the antenna element and the substrate.

FIG. 19 is a graph 1900 from the prior art of electrical resistance (ohms) for multiple test samples using conductive coatings on various papers. Multiple samples were tested, as shown by the X-axis of Graph 1900. Coatings include coated paper (curve 1910), kraft paper (curve 1920), various types of corrugated board (E tier (curve 1930), B tier (curve 1940), and C tier (curve 1950)), as well as commercial use. Printed directly on the label (Curve 1960). This graph 1900 shows that the same conductive coating on different papers has a significant effect on resistance values. With respect to the above equation 1, the efficiency of harvesting largely depends on the resistance value. Experiments have clearly shown that lower resistance values provide better harvesting antenna performance. Materials printed directly on cardboard usually result in higher resistance. In some embodiments of the present disclosure, the use of a particular ink material, which specifically uses the specific carbons described above, solves this problem. In some embodiments, the ink for the antenna material can be tuned to achieve low resistance values for different paper types.

Tuning Circuit In some embodiments, the performance of the energy harvesting circuit or device, or the entire electronic device, is performed continuously or by a predetermined frequency or interval, depending on the energy harvesting optimization procedure. Optimized. Software and / or hardware components of such tuning circuits monitor or determine the absolute input energy level (or the level of electrical power generated from this energy) of the harvested energy. Software and / or hardware components also adjust impedance matching components, antenna components, and load components to perform a search for operational voltages for the highest energy input levels available. .. For example, input / output (I / O) control looking for the highest energy input level available puts the legs of the antenna element, the antenna impedance matching element, the load matching element, or any combination of these elements into the system circuit. It can be done as such or by switching off the circuit, after which the stored energy level and / or the indicator of the amount of reduction is checked, as described above. The configuration of these elements, which leads to the highest energy input level, is thus selected for the operation of the energy harvesting circuit or device, as well as the electronic device as a whole, until the energy harvesting optimization procedure is repeated. The electronic circuit is described with respect to energy harvesting, but in other embodiments, the electronic circuit is specified to be received, such as one designed by a user or a device with which the electronic circuit is associated. You can search for the frequency of.

FIG. 20 shows an embodiment of electronic circuit 2000, including circuits and processors for controlling energy harvesting optimization. The electronic circuit 2000 can be, for example, a microprocessor. The electronic circuit 2000 includes a frequency identification circuit 2010 that identifies a plurality of available frequencies in the surrounding environment and sets a desired frequency based on the power level of the plurality of available frequencies. The electronic circuit 2000 also includes a switching circuit 2020 that communicates with individual connections of the leg elements within the antenna 2050 so as to select or exclude multiple leg elements. Thus, the electronic circuit 2000 has various antenna leg elements and various impedance matching elements that may also be present in the electronic circuit 2000, or load matching elements 2030 which may also be present in the electronic circuit 2000. Switch to on and off (ie, electrically short-circuit and disconnect, or connect in series or in parallel). In this manner, the software and / or hardware components operating under the energy harvesting optimization procedure produce a series of various connection configurations for the antenna leg components. The electronic circuit 2000 can also control impedance matching elements and loads, as well as determine the absolute input energy level of the energy harvested for each configuration. In embodiments where the antenna 2050 is an energy harvesting antenna, the system also includes an energy storage component 2060 that can be used to store the energy received by the antenna 2050. The energy storage component 2060 can be, for example, a battery or a capacitor. The energy storage component 2060 is connected to the device 2070, which is powered by the energy harvested by the antenna 2050.

Switching to include and / or remove these antenna leg elements and impedance matching elements for different configurations achieves reception of different bandwidths and frequencies, as shown in Illustrative Graph 2100 of FIG. .. In FIG. 21, the solid line 2110 and the dashed line 2120 show the results of two exemplary configurations for different maximum energy harvesting situations. The configuration leading to the highest energy input level for a given energy harvesting situation is thus selected for the operation of the energy harvesting circuit or device to which it is powered, and the entire electronic device. The energy harvesting optimization procedure is repeated continuously or regularly. The reason for this is that the energy harvesting situation can potentially change at any given time due to changes in the frequencies available in the surrounding environment or changes in the physical orientation of the antenna. ..

Energy harvesting optimization procedures are useful because the environment in which the energy harvesting circuit or device will be used is usually unknown and potentially variable. Therefore, the frequency of EM radiation that can be used is unknown. EM radiation at any suitable EM frequency may be present in the environment. The two frequencies commonly used in the same environment are 915 MHz and 2.45 GHz, but many other frequency signals may also be present. However, it is not known in advance which frequency will have the signal with the highest amplitude or power level, and thus the best candidate for energy harvesting. At the beginning, for example, the first signal at the first frequency may be present at a very high amplitude or power level, while the second signal at the second frequency is at a much lower amplitude or power level. May have, so that only the first signal is useful for energy harvesting circuits or devices. However, at the second time point, the second signal may be present at a higher amplitude or power level, while the first signal has a lower amplitude or power level, thereby the second. Only the signal of is useful for energy harvesting circuits or devices. At yet another point in time, both signals may be present with useful amplitudes or power levels. In other words, at different times, various combinations of one or more signals at one or more frequencies may be present in the environment at useful amplitudes or power levels.

As a result of the fact that the frequency of the useful signal is unknown, the proper antenna configuration required for maximum energy harvesting capability within any given environment or at any given time point also Similarly, it becomes unknown. The reason for this is that each antenna is usually tuned to receive a signal only at a particular frequency or frequency band. Similarly, the proper impedance (required for impedance matching) of the associated circuit electrically connected to the antenna is also unknown. Therefore, the energy harvesting optimization procedure allows the energy harvesting circuit or device, and / or the associated electronic circuit of the entire electronic device, to be in different combinations or configurations to different antenna and impedance matching elements. It is possible to switch between on and off, which allows the entire antenna to be optimally received for all (or almost all, most, or prominent parts) of the frequencies of useful signals in the environment. Tune. Thereby, the harvesting of useful energy (or the generation of power from this energy) is maximized or optimized for any given situation or environment.

Energy optimization is particularly well suited for embodiments incorporating IC devices. In this embodiment, the electronic device for the energy harvesting circuit or device is in the same IC die and in the same platform packaging, with various logical devices (eg, microprocessors or ASIC devices capable of some processing). ) Is incorporated. Electronic devices for energy harvesting circuits or devices generally include, but are not limited to, impedance matching circuits, rectifier circuits, conditioning circuits, and charge conditioning circuits (eg, capacitors or batteries, etc.). (For devices) is included. Electronic devices for various logical devices are generally, but not limited to, central processing units (CPUs), coprocessors, application specific integrated circuits, and reduced instruction set computing to perform intellectual functions, among others. Ing (RIS)
C) Processors, Advanced RISC Machine (TM) (ARM) processors, and lower level logic. Electronic devices for various logic devices generally include, for example, Bluetooth Low Energy (BLE) standards, Near Field Communication (NFC) protocols, ZIGBEE® clauses, WiFi standards, etc. It can also include communication components such as those related to WIMAX standards and the like.

The embodiments of the disclosed invention are referred to in detail, one or more embodiments thereof are shown in the accompanying drawings. Each embodiment is provided for illustration purposes, not as a limitation of the art. In fact, although this specification is described in detail with respect to specific embodiments of the invention, one of ordinary skill in the art can readily devise changes, modifications, and equalities to these embodiments, provided that the aforementioned description is understood. Please understand that. For example, the features illustrated or described as part of one embodiment may be used in conjunction with another embodiment to obtain further embodiments. For this reason, the subject matter of the present invention is intended to cover all such modifications and variations within the scope of the appended claims and their equality. These and other modifications and variations to the invention may be made by one of ordinary skill in the art without departing from the scope of the invention, which is expressly described by the appended claims. Further, it should be appreciated by those skilled in the art that the above description is merely exemplary and is not intended to limit the invention.

Claims (20)

With the board
An antenna on the substrate comprising the antenna, wherein the antenna comprises a plurality of leg elements, the plurality of leg elements comprising conductive ink and forming a continuous path.
At least one of the plurality of leg elements can be individually selected or excluded so as to change the resonance frequency of the antenna, and the selected leg element has an antenna path length corresponding to the resonance frequency. An antenna system to form. The system of claim 1, wherein the resonant frequency is altered by reducing the antenna path length due to the excluded leg elements being inactive in the plurality of leg elements. The first leg element of the plurality of leg elements has a threshold of the first resonant frequency depending on the received frequency.
The first aspect of claim 1, wherein the first leg element is passively excluded from the antenna path length by being inactive when the received frequency is greater than the threshold of the first frequency. System. The second leg element of the plurality of leg elements has a threshold value of the second resonance frequency depending on the received frequency, and the threshold value of the second resonance frequency is the first resonance frequency. Is greater than the threshold of
The system of claim 3, wherein the second leg element is passively selected by resonance when the received frequency is less than the threshold of the second resonance frequency. The second leg element is passively excluded in addition to the first leg element when the received frequency is greater than the threshold of the second resonant frequency, reducing the antenna path length. The system according to claim 4. The threshold of the first resonant frequency is based on the first electrical impedance of the first leg element.
The threshold of the second resonant frequency is based on the second electrical impedance of the second leg element.
The second electrical impedance is different from the first electrical impedance due to the difference in material properties.
The system of claim 4, wherein the material properties are selected from the group consisting of magnetic permeability, dielectric constant, and conductivity. The system of claim 1, further comprising a printed dielectric element between the two leg elements of the plurality of leg elements. Further comprising an electronic circuit having a connection to each of the plurality of leg elements.
The electronic circuit dynamically shorts the first leg element of the plurality of leg elements with respect to the second leg element, thereby dynamically causing the first leg element of the plurality of leg elements. The system of claim 1, which is configured to be excluded. The electronic circuit
An identification circuit that identifies a plurality of available frequencies in the surrounding environment and sets the resonance frequency based on the power level of the plurality of available frequencies.
A switching circuit that communicates with the connection portion in order to adjust the antenna path length so as to correspond to the resonance frequency by selecting or excluding the leg element from the plurality of leg elements is provided. The system according to claim 8. The substrate comprises a first layer, a second layer laminated on the first layer, and an intermediate layer in the gap between the first layer and the second layer. Ori,
The plurality of leg elements are on the first layer, and the plurality of leg elements form a first antenna arm of the antenna.
The antenna
With the second antenna arm on the second layer,
A conductor on the intermediate layer, wherein the conductor electrically couples the second antenna arm to the plurality of leg elements.
The system according to claim 1, further comprising. 10. The system of claim 10, wherein the substrate is cardboard and the intermediate layer is a wavy intermediate. 10. The tenth aspect of the present invention, wherein the gap between the first layer and the second layer serves as a dielectric between the first antenna arm and the second antenna arm. system. The conductive ink is carbon-based and
The system of claim 1, wherein the substrate comprises paper. The system according to claim 1, wherein the antenna is an energy harvester. A) The board and
An antenna on the substrate, wherein the antenna comprises a plurality of leg elements, the plurality of leg elements containing carbon-based conductive ink and forming a continuous path. Prepare,
Each of the plurality of leg elements can be individually selected or excluded so as to change the resonance frequency of the antenna, and the selected leg elements form an antenna path length corresponding to the resonance frequency. With the antenna system,
B) An electronic circuit having a connection to each of the plurality of leg elements.
The electronic circuit dynamically shorts the first leg element of the plurality of leg elements with respect to the second leg element, thereby dynamically causing the first leg element of the plurality of leg elements. An energy harvesting system comprising said electronic circuits, which are configured to be excluded. The electronic circuit
An identification circuit that identifies a plurality of available frequencies in the surrounding environment and sets the resonance frequency based on the power level of the plurality of available frequencies.
A switching circuit communicating with the connection portion in order to adjust the antenna path length so as to correspond to the resonance frequency by selecting or excluding the leg element from the plurality of leg elements. The system according to claim 15. 16. The system of claim 16, wherein the identification circuit comprises a microprocessor that sets the resonant frequency to be the frequency with the highest power level of the plurality of available frequencies. The substrate comprises a first layer, a second layer laminated on the first layer, and an intermediate layer in the gap between the first layer and the second layer. Ori,
The plurality of leg elements are on the first layer, and the plurality of leg elements form a first antenna arm of the antenna.
The antenna
With the second antenna arm on the second layer,
A conductor on the intermediate layer, wherein the conductor electrically couples the second antenna arm to the plurality of leg elements.
15. The system of claim 15. With the board
An antenna on the substrate, comprising said antenna, wherein the antenna comprises a plurality of leg elements, the plurality of leg elements comprising conductive ink and forming a continuous path.
The first leg element of the plurality of leg elements has a first resonance frequency threshold that depends on the received frequency and the first electrical impedance of the first leg element.
The first electrical impedance is based on material properties selected from the group consisting of magnetic permeability, dielectric constant, and conductivity.
The first leg element can be individually excluded so as to change the resonant frequency of the antenna by changing the antenna path length, with the first leg element having the received frequency being said. An antenna system that is passively excluded from the antenna path length by being inactive if it is greater than the threshold of the first frequency. The second leg element of the plurality of leg elements has a threshold of the received frequency and a second resonance frequency depending on the second electrical impedance of the second leg element.
The second resonance frequency threshold is higher than the first resonance frequency threshold due to the difference in material properties compared to the first leg element.
19. The system of claim 19, wherein the second leg element is passively selected by resonance when the received frequency is less than the threshold of the second resonance frequency.

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